One problem related to manifold/header/muffler/tail pipe has been reported for the 2006 Chrysler 300C. The most recently reported issues are listed below.
My Chrysler 300c hemi started idling rough and showing code p0300. Oil/plugs were changed, and my car worked well for ~500 miles. After which the low oil level light chimmed. After taking to the dealer the oil pressure switch was replaced and all was right. Close to a month later, while stopped at a rail crossing the car stalled with error code p1520. I checked the oil which was low and added to the correct level. In the oil, there was no discoloration or anything to cause alarm. I started the engine up and while the p1520 was gone I had the p0300. After removing the manifold small aluminum pieces where found inside. Plugs that were close to 4k miles old were ash covered and throttle body. Valves and cylinder #3 head need to be replaced.